Study On Cropping System For Water Conservation And Its Assessment In Luoyang City

As the population increases,the situation of water resource crisis and environmentaldeterioration faced by human beings become more and more serious. The water resource crisisbecomes seriously hinderes to the sustainable development of agricultural production. It isn'teffective that the agriculture development rely on consuming water resource and the expend ofirrigation area. To set up a cropping system that is adaptable to the rainfall resources andfavorable to the raise of water use efficiency and ratio is the basic prerequisite to realizesustainable development of agriculture in dry-land regions.The main achievements of the research are as follows:1. On the basis of climate data of Luoyang city in past 49 (1951～2000) years, the rainfalldistribution law with time and space and features was analysed.It was showed that the averageamount of rainfall every ten years is reducing. It was lesser 75.5 mm in 1990s than that in 1960s.The average amount of rainfall in the past 49 years was 688.78 mm. There were 14 lackingrainfall years, 23 ordinary rainfall years and 13 abundant rainfall years during these period. Thefrequency was 28％, 46％and 26％respectively.2. Though analyzing the spatial and temporal change law of soil moisture in Luoyang city, itwas showed that the soil moisture had obviously seasonal and vertical change. In views ofvertical changes of soil moisture, the variation range of upper layers was larger than that oflower.3. The overall and systematic investigation of time-sequence relationship between growth ofdifferent crops and rainfall distribution was did in this paper. And water utilization condition ofdry-land crops was researched.The results showed that from the viewpoint of water adaptability,the autumn crops were better than the summer crops.4. The water equilibrium characters of different cropping system was researched, applyingthe models of water balance in cropland. The research indicated that there was water shortage indifferent cropping system, and the drought became the seriously hindered to the sustainabledevelopment of agricultural production. Under the one crop annual (winter wheat) system, thewater shortage was between 112.2 and 170.1mm, the rainfall satisfaction ratio was between 30.39％and 57.30％, the water satisfaction ratio was bween 59.5％and 73.3％, and the water useefficiency was 15 kg/mm.hm~2. Under the two crops anual (winter wheat-summer corn), the watershortage was 214.8mm, the rainfall satisfaction ratio was 65.1％, the water satisfaction ratio was72.4％, and the water use efficiency was 18.9 kg/mm.hm~2. Under three crops rotation during twoyears (winter wheat-summer corn-spring potato) system, the water shortage was 344.2 mm,the water satisfaction ratio was 76％, and the water use efficiency was 15.7 kg/mm.hm~2 5. The evaluation index system and evaluation method of cropping system that can be usedwidely in dry-land region was established. The target function was to realize the coordinate raiseof social benefit, economic benefit and ecological benefit and to raise the water use efficiency andratio. The Delphi method, experts evaluation method and Analytic Hierarchy Process (AHPmethod) were adopted for it.6. The compositive benefits of four kinds of rotation systems in Luoyang were evaluatedapplying the evaluation model in this paper. The result was winter wheat-summer peanut＞winter wheat-summer corn＞winter wheat-summer corn-spring potato＞winter wheat.7. The analyzing of cropping structure of Luoyang city indicated that the proportions ofcrops area was maladjusted. The proportions of grain crops was much more bigger, while cashcrops was smaller and forage crops was shorted seriously .The cropping dual structure "graincrops-cash crops'was a water-wasting structure with larger area of high water-wasting crops andsmaller area of lower water-wasting crops.8. A multi-objective optimal programming model for water-saving crops planting structurewas first set up in this paper. In the optimized models, the proportions of grain crops, cash cropsand forage crops are adjusted from73.8:24.5:1.7 at present to about 66.9:28.1:5.0 respectively.Through optimizing operation, the new crops planting structure "maintaining grain ration crops;expanding cash crops;increasing forage crops appropriately", have been put forward for dry-landarea of Luoyang city. The coordinate raise of social benefit, economic benefit and ecologicalbenefit would be achieved under the water-saving crops planting structure.The decision system that including the evaluation index system and evaluation method ofcropping system and the multi-objective optimal programming model for water-saving croppingstructure proposed in the paper are of very important theoretic meaning and pratical value.